Dust collectors are desirable and in many cases necessary to remove dust or smoke from the air before discharging the air to the atmosphere. The dust may contain valuable materials to be reclaimed or it may constitute a nuisance if discharged to the atmosphere. Dust collectors in use include various forms of collectors, including cyclones as a form of inertia separator. Other collectors use a filtering process with periodic cleaning of the filter. For high temperature gases, a gravel bed filter (using a loose particulate bed of material) is commonly used and is regenerated by passing clean gas through the bed in a reverse direction at a velocity to separate the accumulated dust from the bed material.